Eustace the Monk - quote Safeguard of the Sea

"The immediate sequel to the French conquests [of Normandy and Anjou 1204] was a war of raiding up and down the Channel, with a particular struggle for the Channel Isles, the last unconquered fragment of the Duchy of Normandy. In this warfare a prominent part was played by the pirate Eustace "the Monk", based of Sark in English service from not later than 1205 to 1215 and thereafter on the side of the baronial rebels and the French.

see

http://pirateshold.buccaneersoft.com/roster/eustace_the_monk.html

http://www.bbc.co.uk/guernsey/content/articles/2004/07/09/timeline_13th_feature.shtml